For over a century, the Jewish World Almanac has been widely regarded as the most authentic source for the worlds Jewish population numbers. Academics all over the world, including the editors of the Encyclopedia Britannica, used to rely on the accuracy of those numbers. Here is what the World Alamanacs of 1933 and 1948 had to say about the world population of Jews.
In other words, according to the World Almanac the world population of Jews increased (!) between 1933 and 1948 from 15,315,000 to 15,753,000. If the German government under Adolf Hitler had as alleged murdered six million Jews those losses should have been reflected in the Jewish population numbers quoted in the World Almanac.